Giardiasis, Emergency Medicine

Basics

Description

Noninvasive diarrhea
Found worldwide:
- 2-15% prevalence in developed nations
- 20-40% prevalence in developing nations
5% of all travelers' diarrhea
Most common intestinal parasite in US:
- Highest incidence in early summer months through fall
- Highest incidence in children aged 1-9 yr and adults aged 30-39 yr
- In 2010, 19,888 cases reported in US (mostly from Northern States)
Fecal-oral transmission:
- Humans are major reservoir
- Zoonotic reservoir in both domestic and wild mammals
- Reservoir in contaminated surface water
Populations at risk:
- Travelers to endemic areas (developing countries, wilderness areas of US)
- Children in day care centers and their close contacts
- Institutionalized persons
- Practitioners of anal sexual activity

Etiology

Giardia lamblia:
- A protozoan flagellate
Also called Giardia intestinalis or Giardia duodenalis
Ingested Giardia attach to intestinal villi
Alters the intestinal brush-border enzymes, impairing digestion of lactose, and other saccharides
No toxin produced

Diagnosis

Signs and Symptoms

History

Onset 1-2 wk postexposure
Infection may be asymptomatic (most common).
Diarrhea of acute onset (90% of symptomatic patients):
- Foul-smelling stools
- Steatorrhea
- Nonbloody
- Self-limiting within 2-4 wk
- More severe in immunocompromised patients and patients with underlying bowel disease
Flatulence and bloating (70-75%)
Abdominal cramping (70%)
Nausea (70%)
Vomiting (30%)
Malaise (86%)
Anorexia (66%)
Weight loss (60-70%)
Fever is rare (15%)
30-50% of acute cases progress to chronic giardiasis (>4 wk):
- Fat malabsorption
- Severe macrocytic anemia secondary to folate deficiency
- Secondary lactase deficiency (in 20-40% of patients)
Infection is more severe and harder to eradicate in immunosuppressed patients.

Acute infection:
- Severe dehydration
Chronic infection:
- Failure to thrive
- Growth retardation and cognitive impairment owing to nutrient malabsorption

Physical Exam

Abdominal exam is benign.
Extraintestinal manifestations (10% of patients):
- Polyarthritis
- Urticaria
- Aphthous ulcers
- Maculopapular rash
- Biliary tract disease

Essential Workup

History:
- Possible sources of exposure
- Membership in high-risk group
Physical exam:
- If gross or occult blood on digital rectal exam, unlikely to be Giardia

Diagnosis Tests & Interpretation

Lab

Stool sample for microscopy (ova and parasites):
- 50-70% sensitive if 1 sample
- 85-90% sensitive if 3 samples taken at 2-day intervals (ideal)
- 100% specific
- Ability to detect other parasites as well
Stool ELISA or immunofluorescent antibody (IFA) assay for Giardia antigen:
- 95% sensitive, 95-100% specific
- Unlike microscopy, cannot rule out other parasites
Stool polymerase chain reaction (PCR):
- 100% sensitive and 100% specific
Fecal leukocytes and stool culture unnecessary unless enteroinvasive organisms suspected (fever, bloody stool)
Serology for anti-Giardia antibodies not helpful in the ED setting
Electrolytes, BUN/creatinine, glucose:
- If prolonged diarrhea or evidence of dehydration
CBC:
- Macrocytic anemia in chronic giardiasis
- Nondiagnostic in acute giardiasis

Imaging
Abdominal CT or ultrasound may show bowel wall thickening and flattened duodenal folds (nonspecific findings)
Diagnostic Procedures/Surgery

Duodenal sampling:
- Entero-Test (patient swallows a weighted string, which is later retrieved and examined for Giardia using microscopy)
Endoscopy:
- Duodenal aspiration
- Endoscopic duodenal biopsy

Differential Diagnosis

Viral gastroenteritis:
- Norwalk virus
- Rotavirus
- Hepatitis A
Bacterial infections:
- Staphylococcus
- Escherichia coli
- Shigella
- Salmonella
- Yersinia
- Campylobacter
- Clostridium difficile
- Vibrio cholerae
Other protozoa:
- Cryptosporidium
- Microsporidia
- Cyclospora
- Isospora
- Entamoeba
Inflammatory bowel disease
Irritable bowel syndrome
Lactase deficiency
Tropical sprue
Drugs and toxins:
- Antibiotics
- Calcium channel blockers
- Magnesium antacids
- Caffeine
- Alcohol
- Sorbitol
- Laxative abuse
- Quinidine
- Colchicine
- Mercury poisoning
Endocrine:
- Addison disease
- Thyroid disorders
Malignancy:
- Colorectal carcinoma
- Medullary carcinoma of the thyroid

Treatment

Initial Stabilization/Therapy

ABCs: Airway, breathing, circulation
IV 0.9% NS if signs of significant dehydration

For severe dehydration (>10%):
- IV bolus with 0.9% NS at 20 mL/kg
- Cardiac monitor
- Blood glucose determination

Ed Treatment/Procedures

Oral fluids for mild dehydration
Correct any serum electrolyte imbalances.
Stool sample for microscopy
If stool sample is positive for Giardia: Treat as listed below under medication
If stool sample negative for Giardia:
- Refer to gastroenterologist for further specialized testing.
- Consider empiric course of metronidazole if high suspicion for Giardia.

Medication

First Line

Metronidazole or tinidazole are the treatment of choice:
- 90% cure rate for each
Metronidazole: 250-500 mg (peds: 15 mg/kg/24h) PO q8h for 5-10 days
Tinidazole: 2 g (peds [>3 yr]: 50 mg/kg) PO once

Second Line
Albendazole (78-90% efficacy), quinacrine (90% efficacy), or nitazoxanide (75% efficacy) if 1st-line therapy fails

Albendazole: 400 mg (peds: 10-15 mg/kg/24h) PO daily for 5-7 days
Furazolidone: 100 mg (peds: 6-8 mg/kg/24h) PO q6h for 7-10 days (not available in US)
Nitazoxanide: 500 mg (peds: 100 mg for ages 2-3 yr, 200 mg for ages 4-11 yr) PO BID for 3 days
Paromomycin: 500 mg (peds: 25-30 mg/kg/24h) PO q8h for 5-10 days
Quinacrine: 100 mg (peds: 6 mg/kg/24h) PO q8h for 5-7 days (limited availability)

Metronidazole is 1st-line therapy (80-95% efficacy)
Alternatives:
- Furazolidone (80-85% efficacy)
- Nitazoxanide (60-80% efficacy)
- Paromomycin (55-90% efficacy)

Metronidazole contraindicated in 1st trimester
Albendazole, quinacrine, and tinidazole are contraindicated throughout pregnancy
Use nitazoxanide instead
If mild symptoms only, consider deferring treatment until late pregnancy or postpartum

Immunocompromised Considerations

Immunocompromised patients at risk for disease that is refractory to standard drug regimens:
- Try drug of a different class/mechanism or metronidazole + quinacrine for at least 2 wk

Use furazolidone in older children only:
- Causes hemolytic anemia in infants
- Causes hemolytic anemia in persons with G6PD deficiency
Avoid quinacrine in G6PD deficiency (causes hemolytic anemia)
Avoid paromomycin in renal failure

Follow-Up

Disposition

Admission Criteria

Hypotension or tachycardia unresponsive to IV fluids
Severe electrolyte imbalance
Children with >10% dehydration
Signs of sepsis/toxicity (rare in isolated giardiasis)
Patients unable to maintain adequate oral hydration:
- Extremes of age, cognitive impairment, significant comorbid illness

Discharge Criteria

Able to maintain adequate oral hydration
Dehydration responsive to IV fluids

Follow-Up Recommendations

Gastroenterology referral for diagnostic endoscopy if symptoms persist for >4 wk despite drug therapy
Acquired lactose intolerance may develop and last for weeks to months
Association with postinfectious fatigue syndrome

Pearls and Pitfalls

Diagnosis is the greatest challenge in this disease:

Include giardiasis in the differential diagnosis of all patients with diarrhea:
- Giardia occasionally reported in domestic water supply
- Patients may not present with the classic history and risk factors to have giardiasis
- 1 stool sample is frequently insufficient for diagnosis

Additional Reading

Escobedo AA, Almirall P, Alfonso M, et al. Treatment of intestinal protozoan infections in children. Arch Dis Child. 2009;94:478-482.
Escobedo AA, Alvarez G, Gonz ¡lez ME, et al. The treatment of giardiasis in children: Single-dose tinidazole compared with 3 days of nitazoxanide. Ann Trop Med Parasitol. 2008;102:199-207.
Escobedo AA, Cimerman S. Giardiasis: A pharmacotherapy review. Expert Opin Pharmacother. 2007;8:1885-1902.
Huang DB, White AC. An updated review on Cryptosporidium and Giardia. Gastroenterol Clin NorthAm. 2006;35:291-314.
Kiser JD, Paulson CP, Brown C. Clinical inquiries. Whats the most effective treatment for giardiasis? J Fam Pract. 2008;57(4):270-272.
Naess H, Nyland M, Hausken T, et al. Chronic fatigue syndrome after Giardia enteritis: Clinical characteristics, disability, and long-term sickness absence. BMC Gastroenterol. 2012;12:13.
Yoder JS, Gargano JW, Wallace RM, et al. Giardiasissurveillance-United States, 2009-2010. MMWR Surveill Summ. 2012;61(5):13-23.

Codes

ICD9

007.1 Giardiasis

ICD10

A07.1 Giardiasis [lambliasis]

SNOMED

58265007 Giardiasis (disorder)

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